Computed tomography (CT) is a medical imaging technique that produces three-dimensional images of internal human body parts from a large series of two-dimensional X-ray images (called profiles) taken in a single-axis rotating structure called a gantry. When compared to a conventional X-ray radiograph, which is an image of many planes superimposed on each other, a CT image exhibits significantly improved contrast.
With the advent of diagnostic imaging systems like CT, where complex and intensive image processing is required, semiconductors play a very important role in developing systems with increased density, flexibility and high performance. The helical or spiral CT machines that use faster computer systems and optimized software can continuously process the cross-section images while the object passes through the gantry at a constant speed.
X-ray slice data is generated using an X-ray source that rotates around the object, with X-ray detectors positioned on the opposite side of the circle from the X-ray source. Many data scans are taken progressively as the patient/object is gradually passed through the gantry. A data acquisition system includes a plurality of detectors or channels.
A detector receives the x-rays attenuated by the patient and generates a corresponding current signal which is further converted to a digital signal. The existing CT systems also utilize spectral information embedded in the received x-rays. Some detectors of the plurality of detectors includes a photon counting system to derive the spectral information. The spectral information represents a variation in the energy (or energy resolution) of the photons received by a detector. The existing photon counting systems include an amplifier of high bandwidth to obtain the spectral information. However, a large amount of power is required to drive the amplifier and to meet a given noise specification. In addition, multiple static comparators are required in the existing photon counting systems which require large power for good energy resolution.